In order for the printed-circuit boards to be populated, the printed circuit boards include a network of printed circuit traces on their bottom side, which functionally interconnect the component connection points provided therein. These printed-circuit boards run on a conveyor belt through the individual processing stations and also pass through devices for fitting the printed-circuit board from above, so-called automatic insertion equipment or SMD-insertion devices, which transport the components to predetermined positions on the top side of the printed-circuit board. For this purpose, the automatic insertion equipment is provided with grippers, which are able to be controlled in a horizontal plane to every point of the printed-circuit board surface. The components, themselves, are stockpiled on a carrier, which in many cases is rolled up into a spool. The components are removed from this carrier, one after another, e.g., by means of a component extractor (suction device) and taken to the designated position.
After all the SMD components required for the circuit arrangements mapped on the printed-circuit board are set down, the components are soldered to their connection points in a soldering station, and the circuit arrangement is then checked for proper functioning.
The desire to keep the overall space required for these circuit arrangements to a minimum has resulted in SMD components being mounted on the bottom side of the printed-circuit boards as well. For this purpose, after leaving the soldering station, the printed-circuit board is lifted off the conveyor belt and is inverted, and the bottom side of the printed-circuit board, now located on top, is provided with an adhesive agent at the surface mounted placements there for the SMD components. The printed-circuit board subsequently passes through second automatic insertion equipment or SMD-insertion devices and the now upwardly pointing bottom side of the printed-circuit board is fitted with other SMD components.
Following the second automatic insertion equipment, the adhesive agent is cured in a hardening station, so that the components adhere securely to the printed-circuit board; the printed-circuit board is then inverted again and subsequently run through a wave-soldering station to solder the components on the bottom side to the printed circuit traces.
In some instances, components, which are not able to be manipulated using a component extractor (suction device), are even placed beforehand by hand on the top side of the printed-circuit board.